File & Media Thunder


File Thunder — Architecture & Design Guide

File Thunder — Architecture & Design Guide

NexGate Media Engine | Version 1.0

Table of Contents

  1. What is File Thunder?
  2. The Four Wheels
  3. Storage Architecture (MinIO Buckets)
  4. Accepted File Formats
  5. Upload Flow
  6. Processing Pipelines
  7. Watermarking Strategy
  8. File Protection Layers
  9. URL Strategy
  10. OG (Open Graph) Strategy
  11. Compression & Transcoding
  12. BlurHash, LQIP & Dominant Color
  13. Deduplication
  14. Quota Management
  15. Storage Lifecycle
  16. Abandoned Upload Handling
  17. Progress Tracking (SSE)
  18. Communication Architecture
  19. CDN Strategy
  20. Shareable Links
  21. Technology Stack
  22. Database Schema
  23. Docker & Infrastructure
  24. What File Thunder Does NOT Do

1. What is File Thunder?

File Thunder is NexGate's dedicated media processing engine. It is a standalone Spring Boot microservice responsible for all file and media operations across the entire NexGate platform.

Core principle: The Main Backend never touches raw files. It delegates all media operations to File Thunder and acts as a thin client.

Responsibilities:

What it is NOT:

2. The Four Wheels

File Thunder is powered by four core engines:

FILE THUNDER ENGINE
           │
    ┌──────┼──────┬──────┐
    │      │      │      │
 FFmpeg    IM   ClamAV  MinIO
 Video   Image  Sec    Storage
 Wheel   Wheel  Wheel   Wheel

Wheel 1 — FFmpeg (Video)

Java wrapper: Jaffree (calls /usr/bin/ffmpeg via ProcessBuilder)

Wheel 2 — ImageMagick (Images)

Java wrapper: IM4Java (calls /usr/bin/convert via ProcessBuilder)

Additional library: blurhash-java for BlurHash generation

Wheel 4 — MinIO (Storage)

Java SDK: MinIO Java SDK (io.minio:minio)

Wheel 3 — ClamAV (Security)

Java client: clamd4j or custom TCP socket client

3. Storage Architecture (MinIO Buckets)

Rule: 4 buckets total. Never one bucket per user.

nexgate-raw/          ← temporary upload landing zone
nexgate-public/       ← CDN cached, social content
nexgate-private/      ← signed URLs, DMs + docs
nexgate-digital/      ← purchase-gated, digital products

nexgate-raw (Temporary)

nexgate-raw/
  uploads/{userId}/{fileId}/
    original.ext     ← raw upload lands here

nexgate-public

nexgate-public/
  profiles/{userId}/{fileId}/
    avatar_400.webp
    avatar_150.webp
    avatar_50.webp
    cover.webp

  posts/{userId}/{fileId}/
    360p_clean.mp4
    720p_clean.mp4
    1080p_clean.mp4
    360p_watermarked.mp4
    720p_watermarked.mp4
    1080p_watermarked.mp4
    preview_3s.mp4
    hls/master.m3u8
    hls/360p/segment_000.ts ...
    hls/720p/segment_000.ts ...
    thumbnail.webp
    og_clean.webp
    og_play.webp
    og_preview.mp4

  stories/{userId}/{fileId}/
    720p_clean.mp4
    thumbnail.webp

  events/{accountId}/{eventId}/{fileId}/
    banner.webp
    banner_mobile.webp
    banner_thumb.webp

  shops/{shopId}/{productId}/{fileId}/
    large.webp
    medium.webp
    thumb.webp

  categories/{categoryId}/{fileId}.webp

nexgate-private

nexgate-private/
  messages/{conversationId}/{fileId}/
    original.jpg
    thumb.webp

  audio/{fileId}.wav      ← temp for Rec Engine (deleted after transcription)

  documents/{userId}/{fileId}/
    original.pdf
    preview.webp

  kyc/{userId}/{fileId}/
    id_front.jpg
    id_back.jpg

nexgate-digital

nexgate-digital/
  products/{shopId}/{productId}/{fileId}/
    original/
      file.pdf           ← actual purchased product
      checksum.txt       ← SHA-256 hash
    preview/
      preview.webp       ← low-res watermarked preview
      cover.webp         ← product cover image

Object Key Pattern (Consistent Rule)

{bucket}/{domain}/{ownerId}/{entityId}/{fileId}/{variant}

Examples:
nexgate-public/posts/usr_123/post_456/file_789/thumb.webp
nexgate-private/messages/conv_abc/file_789/original.jpg
nexgate-digital/products/shop_xyz/prod_123/file_789/original.pdf

4. Accepted File Formats

Images

Accept Reject
JPEG/JPG BMP
PNG TIFF
HEIC/HEIF RAW
WebP SVG (security risk)
GIF

Output: Always WebP

Videos

Accept Reject
MP4 WMV
MOV FLV
MKV VOB
WEBM
AVI
3GP

Output: H.264 MP4 (short) or HLS H.264 (long)

Digital Products

PDF, DOCX, XLSX, PPTX, GLB, OBJ, FBX, STL, MP3, WAV, FLAC, ZIP, RAR, PSD, AI, PNG (stock art)

5. Upload Flow

Step-by-Step

CLIENT
  ↓
[1] Intelligent client-side compression
    - Detect: resolution, bitrate, codec, network type, device tier
    - Compress if: over-bitrated, slow network, large file
    - Never compress if: already optimized
    - Target: max 1080p, CRF 18 (light)
    - HEIC → JPEG conversion (iOS)
  ↓
[2] POST /media/upload-request
    {
      fileName, fileSize, mimeType,
      directory, clientMeta: {
        clientApp, networkType,
        deviceTier, wasCompressed
      }
    }
  ↓
[3] File Thunder validates:
    - MIME type in allowed list?
    - File size within per-upload limit?
    - User quota not exceeded? (atomic SQL check)
    - Creates DB record: status PENDING
    - Generates presigned MinIO URL → nexgate-raw
    - Returns { fileId, uploadUrl, expiresIn: 1800 }
  ↓
[4] Client uploads directly to MinIO
    - TUS resumable protocol for large files
    - Multipart upload for files > 5MB
    - Progress tracked client-side
    - Upload starts during caption writing (parallel)
  ↓
[5] Client confirms: POST /media/confirm { fileId }
    (or cleanup job recovers if confirm missed)
  ↓
[6] Processing pipeline starts

Quota + Duration Enforcement

Size check → at presigned URL generation (before upload):

Atomic SQL:
  UPDATE user_storage_quota
  SET used_bytes = used_bytes + fileSize
  WHERE user_id = ?
  AND (used_bytes + fileSize) <= quota_bytes
  RETURNING used_bytes

  0 rows affected → quota exceeded → reject 403
  1 row affected  → quota reserved → proceed

Duration check → after upload (FFprobe analysis):

Client sends estimated duration in clientMeta (hint only)
FFprobe confirms actual duration after upload

If actual duration > plan limit:
  → delete file from nexgate-raw
  → reject with 403: { error: "DURATION_EXCEEDED", plan: "FREE", maxDuration: 300 }
  → release quota reservation
  → notify user: "Upgrade plan to upload longer videos"

Why duration checked after upload (not before):

Client-reported duration = not trusted
  = could be manipulated
FFprobe = ground truth
  = server side, reliable
  = only way to confirm actual duration

Per-Upload Size + Duration Limits

Plan Image Short Video (social) Long Video Digital Product Video Duration
FREE 20MB 200MB ❌ Not allowed ❌ Not allowed Max 5 min
PRO 20MB 500MB 2GB 5GB per file Max 60 min
BUSINESS 20MB 2GB 5GB 20GB per file Unlimited

Why duration matters as much as size:

Same 200MB could be:
  3 minute 1080p reel   → acceptable ✅
  45 minute long video  → not acceptable for FREE ❌

Size check alone = not enough
Duration check = required alongside size

Enforcement:
  Size  → checked at upload request (before presigned URL)
  Duration → checked AFTER upload (FFprobe analysis)
             client also sends estimated duration in clientMeta
             
  If duration exceeds plan limit after FFprobe:
    → delete from nexgate-raw
    → reject processing
    → notify user: "Upgrade to upload longer videos"
    → refund quota reservation

Duration limits by plan:

FREE:
  Reels/short video → max 5 minutes
  Long video        → not allowed
  
PRO:
  Reels/short video → max 5 minutes (treated as short)
  Long video        → max 60 minutes
  
BUSINESS:
  All video         → unlimited duration

6. Processing Pipelines

6.1 Image Pipeline

Upload confirmed
  ↓
RabbitMQ: SCAN job
  ↓
ClamAV scan → VIRUS: quarantine + notify | CLEAN: continue
  ↓
SHA-256 hash check (deduplication)
  Exists + clean → skip processing, reuse variants
  New → continue
  ↓
RabbitMQ: PROCESS job → Image Worker
  ↓
[1]  Auto-orient (apply EXIF rotation before stripping)
[2]  Extract useful EXIF (orientation only)
[3]  Strip ALL EXIF (privacy — remove GPS, device info)
[4]  AI moderation check (NSFW detection)
     UNSAFE → quarantine | SAFE → continue
[5]  Extract dominant color (resize to 1×1 pixel)
[6]  Generate LQIP (resize to 10×10, base64 encode)
[7]  Generate BlurHash (blurhash-java library)
[8]  Generate variants by content type:
     Profile   → 400px, 150px, 50px (WebP)
     Post      → 1600px, 800px, 300px (WebP)
     Product   → 1000px, 500px, 200px (WebP, 1:1 square)
     Event     → 1200×630px, 800×420px (WebP)
     Story     → 1080×1920px (WebP)
[9]  Convert all variants → WebP
[10] Generate OG image (1200×630, WebP):
     - og_clean.webp (no play button)
     - For non-16:9 → blur pad background to fill 16:9
[11] Store all variants → nexgate-public
[12] Delete original from nexgate-raw
[13] Update DB: status READY, populate variants JSONB
[14] Publish to Kafka: FILE_READY event
[15] Publish to RabbitMQ: MEDIA_READY event → Main Backend

Variant sizes per content type:

Content Variants
Profile picture 400px, 150px, 50px
Post image 1600px (large), 800px (medium), 300px (thumb)
Product image 1000px, 500px, 200px (always 1:1 square)
Event banner 1200×630, 800×420, 400×210
Category 400px wide

6.2 Short Video Pipeline (MP4)

Threshold: Duration < 3 minutes → MP4

Upload confirmed
  ↓
RabbitMQ: SCAN job
  ↓
ClamAV scan → VIRUS: quarantine | CLEAN: continue
  ↓
SHA-256 hash check (deduplication)
  ↓
FFprobe analysis:
  - resolution, bitrate, fps
  - codec, duration, aspectRatio
  - hasAudio, qualityScore
  ↓
Adaptive transcode decision:
  - Never upscale (never exceed input resolution)
  - Never inflate (if output > input size, use original)
  - Only generate eligible variants
  ↓
RabbitMQ: PROCESS job → Video Worker
  ↓
[FAST LANE — runs first for UX]:
  Quick 360p transcode → post goes LIVE_PARTIAL
  User notified: "Almost ready!"
  ↓
[FULL PROCESSING — continues async]:
[1]  Detect aspect ratio (FFprobe):
     9:16  (vertical)  → native reel format → no padding needed
     16:9  (landscape) → needs blur pad for reel pool
     1:1   (square)    → needs blur pad for reel pool
     4:5   (portrait)  → needs blur pad for reel pool
     Other             → preserve original, blur pad if reel eligible

[2]  Transcode CLEAN variants (H.264, faststart):

     For NATIVE 9:16 videos:
       Transcode directly to 9:16 variants
       360p_clean.mp4  (360×640,  CRF 28)
       720p_clean.mp4  (720×1280, CRF 23)
       1080p_clean.mp4 (1080×1920, CRF 21, if eligible)

     For NON-9:16 videos (isReelEligible = true):
       Apply BLUR PAD to fill 9:16 frame (TikTok/Instagram style)

       What blur pad looks like:
       ┌──────────────┐
       │▓▓▓▓▓▓▓▓▓▓▓▓▓│  ← blurred background (scaled up + blurred)
       │▓▓▓▓▓▓▓▓▓▓▓▓▓│
       │┌────────────┐│
       ││            ││
       ││  original  ││  ← actual video centered (no cropping)
       ││   video    ││
       ││            ││
       │└────────────┘│
       │▓▓▓▓▓▓▓▓▓▓▓▓▓│
       │▓▓▓▓▓▓▓▓▓▓▓▓▓│
       └──────────────┘

       Why blur pad (not black bars, not crop):
         Black bars → looks amateur ❌
         Crop → destroys content ❌
         Blur pad → professional, intentional ✅
                    TikTok + Instagram do this ✅
                    No content lost ✅

       FFmpeg blur pad command:
       ffmpeg -i input.mp4 \
         -filter_complex \
         "[0]scale=720:1280:force_original_aspect_ratio=increase,
          crop=720:1280,
          boxblur=20:5[bg];
          [0]scale=720:1280:force_original_aspect_ratio=decrease,
          pad=720:1280:(ow-iw)/2:(oh-ih)/2[fg];
          [bg][fg]overlay=(W-w)/2:(H-h)/2" \
         output_9_16_blurpad.mp4

       Steps:
         bg layer → scale to FILL 9:16, crop excess, apply blur (20px radius)
         fg layer → scale to FIT in 9:16, letterbox, center
         overlay  → sharp video (fg) on top of blurred background (bg)

     For NON-9:16 videos (isReelEligible = false):
       Keep original aspect ratio
       No blur pad
       Feed player handles letterboxing client-side

[3]  Generate WATERMARKED variants:
     FFmpeg overlay — MOVING watermark (TikTok style):
       Watermark jumps between corners every 3 seconds:
         0-3s  → top left     (10px, 10px)
         3-6s  → top right    (W-w-10, 10px)
         6-9s  → bottom right (W-w-10, H-h-10)
         9-12s → bottom left  (10px, H-h-10)
         repeat...
       Logo PNG: 80×80px, 60% opacity
       Username text: same position as logo (below it)
       Based on clientApp field:
         NEXGATE_ANDROID / NEXGATE_IOS / NEXGATE_WEB → "NexGate"
         NEXGATE_LITE → "NexGate Lite"

     Why moving watermark:
       Static corner = easy to crop out ❌
       Moving = appears in all corners = impossible to crop ✅
       TikTok confirmed uses this strategy

     FFmpeg command (moving watermark):
       overlay=
         x='if(lt(mod(t,12),3), 10,
            if(lt(mod(t,12),6), W-w-10,
            if(lt(mod(t,12),9), W-w-10, 10)))':
         y='if(lt(mod(t,12),3), 10,
            if(lt(mod(t,12),6), 10,
            if(lt(mod(t,12),9), H-h-10, H-h-10)))'

     Variants generated:
     360p_watermarked.mp4
     720p_watermarked.mp4
     1080p_watermarked.mp4

[4]  Generate extras:
     thumbnail.webp     → best frame (brightness + sharpness scored)
     thumbnail LQIP     → 10×10 base64
     thumbnail BlurHash → blurhash-java
     thumbnail dominantColor → hex
     preview_3s.mp4     → first 3 seconds, 360p, muted, watermarked
     og_clean.webp      → 1200×630, clean thumbnail
     og_play.webp       → 1200×630, NexGate play button burned in
     og_preview.mp4     → 360p, watermarked, permanent CDN URL

[5]  Generate Fragmented MP4 (fMP4):
     ffmpeg flags: frag_keyframe+empty_moov+faststart
     1-second fragment intervals (keyframe every 30 frames at 30fps)
     Enables byte-range requests for progressive streaming

[6]  Extract audio for Rec Engine:
     ffmpeg -vn -acodec pcm_s16le -ar 16000 -ac 1 audio.wav
     Store → nexgate-private/audio/{fileId}.wav
     (Rec Engine fetches, transcribes, deletes)

[7]  Store all variants → nexgate-public
[8]  Delete original from nexgate-raw
[9]  Update DB:
     status: READY
     isReelEligible: true (duration < 3min)
     streamingFormat: MP4
     variants: JSONB with all paths
     aspectRatio, qualityScore, duration
[10] Publish to Kafka: FILE_READY (with audioRef)
[11] Publish to RabbitMQ: MEDIA_READY → Main Backend
     Main Backend:
       → update post status LIVE
       → index into reel pool
       → trigger fan-out to followers

Reel pool eligibility:

duration < 3 minutes → isReelEligible: true → indexed in reel pool
duration ≥ 3 minutes → isReelEligible: false → feed only

MP4 variant resolutions by aspect ratio:

Aspect 360p 540p 720p 1080p
9:16 (vertical) 360×640 540×960 720×1280 1080×1920
16:9 (landscape) 640×360 — 1280×720 1920×1080
1:1 (square) 360×360 — 720×720 1080×1080

Why 1080p is max (not 4K):

All major platforms compress 4K down to 1080p on delivery anyway:

Accepting 4K but processing/serving max 1080p = correct strategy. Above 1080p = no visible benefit for social content, just wasted storage.

Platform max resolution reference (2026):

Platform Max Resolution Aspect Max File Size
TikTok 1080×1920 9:16 287MB mobile / 4GB web
Instagram Reels 1080×1920 9:16 4GB
YouTube Shorts 1080×1920 9:16 —
Facebook Reels 1080×1920 9:16 1GB
Twitter/X 1280×1024 any 512MB

Safe zone for 9:16 reels (1080×1920):

┌──────────────────┐
│░░░░ top 120px ░░░│ ← UI bar — avoid placing content here
│                  │
│   SAFE ZONE      │ ← faces, text, important content here
│   860×1550px     │
│                  │
│░ right 180px ░░░░│ ← action buttons (like, comment, share)
│░░ bottom 250px ░░│ ← caption area
└──────────────────┘

Watermark placement must respect safe zones.

6.3 Long Video Pipeline (HLS)

Threshold: Duration ≥ 3 minutes → HLS

Same as short video EXCEPT:

Format → HLS adaptive streaming (not MP4)
No fast lane (too long, post stays PROCESSING)
Post goes live only when fully processed

Transcode to HLS:
  hls/360p/  → segments + 360p.m3u8
  hls/720p/  → segments + 720p.m3u8
  hls/1080p/ → segments + 1080p.m3u8
  hls/master.m3u8 → points to all quality manifests

Segment duration: 2 seconds
Codec: H.264, AAC audio
Container: MPEG-TS (.ts chunks)

Still generated:
  preview_3s.mp4     ← for feed inline autoplay
  thumbnail.webp
  LQIP, BlurHash, dominantColor
  og_clean.webp, og_play.webp, og_preview.mp4

isReelEligible: false
streamingFormat: HLS

HLS Cache-Control:

.ts chunks:    Cache-Control: public, max-age=31536000
master.m3u8:   Cache-Control: public, max-age=31536000

6.4 Digital Products Pipeline

Upload Processing

Seller uploads product file
  ↓
Validate:
  - File type allowed?
  - Seller quota OK?
  - Product exists + owned by seller?
  ↓
ClamAV scan (DOUBLE scan — extra safety)
  ↓
SHA-256 checksum generated + stored
  ↓
Light processing by file type:

  PDF:
    Extract page 1 → preview image (72 DPI)
    Watermark "PREVIEW" across image
    Store: preview/preview.webp

  Video course (MP4):
    Extract first 2 minutes
    Transcode to 480p
    Watermark burned in
    Store: preview/preview.mp4

  Audio (MP3/WAV/FLAC):
    Extract first 30 seconds
    Lower bitrate (96kbps)
    Store: preview/preview.mp3

  3D Models (GLB/OBJ/FBX):
    Render thumbnail from multiple angles
    Store: preview/thumb_*.webp

  Images (stock art, PNG):
    Resize to low resolution (600px max)
    "PREVIEW" watermark burned in
    Store: preview/preview.webp

  Software/ZIP:
    No preview file
    Cover image only

  ↓
Store → nexgate-digital/products/{shopId}/{productId}/{fileId}/
  original/ ← actual product (never exposed publicly)
  preview/  ← shown to everyone
  cover/    ← product listing thumbnail
  ↓
Update DB: READY
Publish to RabbitMQ: DIGITAL_PRODUCT_READY → Main Backend

Download Flow (Buyer)

Buyer clicks Download
  ↓
POST /digital/download { productId, orderId, fileId }
  ↓
File Thunder validates:
  [1] orderId exists in DB?
  [2] orderId belongs to requesting user?
  [3] Order status = PAID?
  [4] download_count < download_limit?
  [5] Current time < expires_at?
  [6] User account in good standing?
  ↓
All pass:
  Generate single-use signed URL:
    10-minute TTL
    Order bound
    Device bound
    Encrypted token
    Stored in Redis (single-use enforcement)
  ↓
Log download event:
  orderId, buyerId, timestamp
  IP address, deviceId, country
  ↓
Increment download_count
  ↓
Return signed URL to client
Client downloads (chunked, resumable via byte-range)
  ↓
URL marked as used in Redis → 403 on reuse

No forensic watermarking for now. Planned for future phase when piracy becomes a real problem.

6.5 DM Attachments Pipeline

Same core pipeline with different rules:

Social Posts DM Attachments
Bucket nexgate-public nexgate-private
CDN ✅ Cloudflare ❌ No CDN
Access check Public/followers Conversation membership
Variants Full (all sizes) Thumb + original only
Watermark ✅ On download ❌ Never
Reel pool ✅ If eligible ❌ Never
Virus scan ✅ Yes ✅ Yes
URL type Permanent CDN Signed 5min TTL
Processing Full Minimal

Access control for DM files:

Client requests DM file URL
  ↓
File Thunder checks:
  Is requesting user a member of this conversation?
  YES → generate signed URL (5min TTL)
  NO  → 403 Forbidden

7. Watermarking Strategy

When Applied

When Served

Scenario Variant Served
Watching on NexGate (in-app/web) Clean variant
Downloading via NexGate download button Watermarked variant
Accessing via CDN URL directly Clean variant (unavoidable)
Sharing via savefromnet-style tools Clean variant (acceptable)

Watermark Position — Moving (TikTok Style)

Jumps between 4 corners every 3 seconds:
  0-3s  → top left
  3-6s  → top right
  6-9s  → bottom right
  9-12s → bottom left
  repeat for full video duration

Logo: 80×80px, 60% opacity
Username: directly below logo, same position

Why moving:
  Static corner → easy to crop out ❌
  Moving → appears everywhere → impossible to crop ✅
  TikTok confirmed uses this strategy

App-based Watermark

clientApp = NEXGATE_ANDROID → "NexGate" logo
clientApp = NEXGATE_IOS     → "NexGate" logo
clientApp = NEXGATE_WEB     → "NexGate" logo
clientApp = NEXGATE_LITE    → "NexGate Lite" logo

Determined at upload time. Burned at processing time. Never changes.

Pre-Watermarked Content (Uploaded from Other Platforms)

The Problem:

User downloads TikTok video (has TikTok watermark)
Re-uploads to NexGate
NexGate adds NexGate watermark on top
= two watermarks visible = bad UX 😂

What major platforms do:

Platform Approach
Instagram Algorithm suppresses watermarked content from discovery
TikTok No detection, just adds own watermark on top
YouTube Shorts Suppresses competitor watermarked content

Instagram head Adam Mosseri confirmed: videos with competitor watermarks receive significantly reduced algorithmic reach.

NexGate approach by phase:

Phase 1 (launch — current):
  No watermark detection at all
  NexGate watermark burned on top of everything
  Pre-existing watermarks = overwritten/overlaid
  = zero complexity ✅
  = same pipeline for all videos ✅
  = double watermark acceptable at this stage ✅

Phase 2 (growth):
  Client-side warning before upload:
  "This video appears to have a watermark
   from another platform. Remove it for
   better reach on NexGate."
  User can proceed anyway
  = user educated, NexGate protected ✅

Phase 3 (scale):
  Server-side AI detection:
    Scan first frame for known platform logos
    Flag: hasExternalWatermark: true
    Suppress in reel pool (isReelEligible: false)
    Show post-level label: "Cross-posted content"
    = same approach as Instagram ✅

Note: NexGate never BLOCKS pre-watermarked uploads. Only suppresses reach in discovery/recommendations. Content still visible to uploader's followers.

Username Change Policy

Old videos keep old username watermark (same as TikTok). Re-watermarking = future premium feature.

8. File Protection Layers

Layer Method Stops
1 Content-Disposition: inline header Casual right-click downloaders
2 Dynamic URL via JS (never in HTML) HTML source inspection
3 Signed expiring URLs (private content) URL sharing between users
4 Session + device binding Cross-device URL reuse
5 Disable right-click on player (frontend) Non-technical users
6 Watermark burned on download Casual sharing without credit
7 HLS chunking for video Download and reassembly

Philosophy: Goal is not impossible to download. Goal is not worth the effort for 99% of users + traceable if they do.

9. URL Strategy

Public Content → Permanent CDN URLs

Thumbnail:
https://media.nexgate.com/posts/usr_123/vid_789/thumb.webp

Video (public, clean):
https://media.nexgate.com/posts/usr_123/vid_789/720p_clean.mp4

OG preview (permanent):
https://media.nexgate.com/og/vid_789/og_preview.mp4

Profile picture:
https://media.nexgate.com/profiles/usr_123/avatar_400.webp

Private Content → Signed Expiring URLs

DM attachment:
https://media.nexgate.com/private/...?
  x-expires=1716305400
  &x-sig=hmac_signature
  &x-uid=usr_xyz
  &x-sid=sess_abc

Digital product download:
https://media.nexgate.com/digital/...?
  x-expires=1716305400
  &x-sig=hmac_signature
  &x-order=enc_orderId
  &x-device=device_abc

Signed URL Params Explained

Param Purpose Without It
x-expires URL dies after TTL Permanent link = unrevokable
x-sig HMAC tamper protection Anyone can forge expiry
x-uid Bound to user session URL shareable between users
x-sid Bound to session Works after logout

Who Generates vs Validates

TTL by Content Type

Content TTL
Stream URL (video) 10 min
DM attachment 5 min
Digital product download 10 min (single-use)
Public CDN content Permanent
OG preview video Permanent

10. OG (Open Graph) Strategy

For Video Posts

<meta property="og:type" content="video.other" />
<meta property="og:url" content="https://nexgate.com/reels/reel_abc123" />
<meta property="og:title" content="@username on NexGate" />
<meta property="og:description" content="caption text..." />

<!-- Clean thumbnail (permanent CDN) -->
<meta property="og:image"
  content="https://media.nexgate.com/posts/usr_123/vid_789/thumb.webp" />
<meta property="og:image:width" content="1200" />
<meta property="og:image:height" content="630" />
<meta property="og:image:type" content="image/webp" />

<!-- Permanent OG preview video (NOT signed, NOT expiring) -->
<meta property="og:video"
  content="https://media.nexgate.com/og/vid_789/og_preview.mp4" />
<meta property="og:video:type" content="video/mp4" />
<meta property="og:video:width" content="360" />
<meta property="og:video:height" content="640" />

<meta property="og:site_name" content="NexGate" />

<!-- Twitter Card -->
<meta name="twitter:card" content="player" />
<meta name="twitter:image"
  content="https://media.nexgate.com/posts/usr_123/vid_789/thumb.webp" />
<meta name="twitter:player"
  content="https://nexgate.com/embed/reel_abc123" />

For Image Posts

<meta property="og:type" content="website" />
<meta property="og:image"
  content="https://media.nexgate.com/posts/usr_123/img_789/og.webp" />
<!-- No og:video tag = no play button shown -->

Play Button Behavior

Platform Play Button Source
WhatsApp Added by WhatsApp (reads og:type)
Telegram Added by Telegram
Twitter/X Added by Twitter
SMS/Email Must burn into og:image (og_play.webp)
Unknown apps Must burn into og:image (og_play.webp)

NexGate serves og_clean.webp to known platforms, og_play.webp to unknown platforms (detected via crawler User-Agent).

OG Video URL — Why Permanent

11. Compression & Transcoding

Client-Side Intelligent Compression

Before upload, client analyzes:

Inputs:
  resolution, bitrate, codec
  network type (WiFi/4G/3G/2G)
  device tier (high/mid/low)

Decision:
  Already optimized + good network → upload direct
  Over-bitrated → compress
  Slow network → compress regardless

Target (if compressing):
  Max 1080p
  CRF 18 (light — preserve quality for server)
  H.264

Never upscale on client either.

Server-Side Adaptive Transcoding

After upload, FFprobe analyzes:

Extract: width, height, bitrate, fps, codec, duration

Decision tree:
  height ≥ 1080 → generate 1080p, 720p, 360p
  height ≥ 720  → generate 720p, 360p
  height ≥ 480  → generate 480p, 360p
  height < 480  → keep original resolution

Rules:
  NEVER upscale (never exceed input resolution)
  NEVER inflate (if output > input size → use original as-is: -c:v copy)
  CRF adapts to input quality

CRF Values (H.264)

Variant CRF Use
1080p 21 High quality
720p 23 Standard
480p 25 Medium
360p 28 Low / slow networks
OG preview 30 Very small file

Video Codec Strategy

Now Future
H.264 (universal support) AV1 (50% smaller, open source)
AAC audio 128kbps Opus audio
MP4 container CMAF container

Image Format Strategy

Input Output
JPEG WebP (quality 80%)
PNG WebP (quality 85%)
HEIC WebP (quality 80%)
GIF WebP animated + MP4 loop

Critical FFmpeg Flags

-movflags +faststart  → metadata at start of file
                        = video starts playing before fully downloaded
                        = essential for web streaming

-movflags frag_keyframe+empty_moov+faststart  → fragmented MP4
                        = byte-range requests work
                        = reel prefetch works

Generation Loss (Double Compression)

12. BlurHash, LQIP & Dominant Color

All three generated for every image and video thumbnail:

Dominant Color

ImageMagick resize to 1×1 pixel
→ average color of entire image
→ stored as hex: "#2D7BC8"
→ shown instantly as CSS background (0ms, 0 bytes extra)

BlurHash

Algorithm: DCT-based image encoding
Output: ~30 character string "LGF5]+Yk^6#M@-5c,1J5@[or[Q6."
Library: blurhash-java
Components: 4x3 (width x height)
→ decoded client-side to blurry placeholder
→ no network request
→ shows shape/composition of image

LQIP (Low Quality Image Placeholder)

ImageMagick resize to 10×10px
Quality: 20%
Convert to base64 string
→ embedded in feed JSON
→ client scales up (naturally blurry)
→ more accurate than BlurHash
→ no network request

Progressive Loading Stages

Stage 0 (instant, 0ms):  dominantColor CSS background
Stage 1 (instant, 0ms):  BlurHash decoded → blurry shape
Stage 2 (instant, 0ms):  LQIP scaled up → accurate blur
Stage 3 (CDN, 50-200ms): thumb.webp loads → sharp thumbnail
Stage 4 (on demand):     large.webp loads → full quality (on tap)

13. Deduplication

Hash-Based (Exact Match)

File uploaded
  ↓
Compute SHA-256 of raw file
  ↓
Check file_hashes table:
  HASH EXISTS + was CLEAN → skip processing entirely
                            create reference to existing variants
                            increment reference_count
  HASH NOT FOUND → process normally
                   save hash + object_key to file_hashes

Benefits

Reference Counting (Deletion)

User deletes file
  ↓
Decrement reference_count
reference_count > 0 → keep file (others reference it)
reference_count = 0 → delete from MinIO

Near-Duplicate Detection

14. Quota Management

Enforcement Point

At presigned URL generation — never after upload.

Request upload
  ↓
Atomic check:
  UPDATE user_storage_quota
  SET used_bytes = used_bytes + fileSize
  WHERE user_id = ?
  AND (used_bytes + fileSize) <= quota_bytes
  RETURNING used_bytes

  0 rows affected → quota exceeded → reject with 403
  1 row affected  → quota reserved → proceed

What Counts Against Quota

Content Charged
Social posts Original upload size only
Digital products Actual stored bytes (all variants)

Plan Limits

Plan Storage Max Image Max Video
FREE 1GB 20MB 200MB, 5min
PRO 20GB 20MB 1GB, 60min
BUSINESS 100GB 20MB 2GB, unlimited

Warning System

80% used → email + in-app notification
95% used → in-app banner
100% used → uploads blocked, existing content untouched

Quota Release

Quota Cache (Redis)

GET quota:usr_123 → used_bytes (cached)
INCRBY quota:usr_123 fileSize → atomic increment
Sync to PostgreSQL every 5 minutes

15. Storage Lifecycle

nexgate-raw

Auto-delete: 24 hours (MinIO lifecycle policy)
Incomplete multiparts: aborted after 24 hours

nexgate-public (Social Content)

All variants: keep FOREVER (never delete)
Move to cold storage tier based on access frequency:
  Hot  (< 30 days or high views)   → NVMe SSD
  Warm (30-365 days, moderate)     → HDD
  Cold (1yr+, rare access)         → Cold object tier
  
CDN serves from cache after first request
MinIO barely hit after content warms up

Smart lifecycle (access-based, not just age):
  < 100 views/day for 30 days → move to warm
  < 10 views/day for 90 days  → move to cold
  Viral spike on old content  → auto-promote back to hot

nexgate-private

DM attachments: 1 year
Audio temp files (for Rec Engine): 24 hours OR deleted by Rec Engine after transcription
KYC documents: per legal requirement

nexgate-digital

Original product files: FOREVER (seller's product)
Preview files: FOREVER
Cover images: FOREVER

Deleted Content (Soft Delete)

User deletes post
  ↓
DB: soft delete (mark deleted, keep record)
  ↓
30-day grace period:
  User can appeal/restore
  Legal holds possible
  CDN cache still valid (purge takes time)
  ↓
30 days → hard delete from MinIO
           Cloudflare cache purge
           DB record updated
           Quota freed

16. Abandoned Upload Handling

The Problem

File uploaded to nexgate-raw ✅
Client never sends POST /media/confirm ❌
Reasons: app crash, network drop, user closed app
→ file stuck in raw bucket = wasted storage

Three-Layer Solution

Layer 1 — Client Confirm (Primary fast path)

Client sends POST /media/confirm after upload
→ processing triggered immediately
→ best UX (instant)

Layer 2 — Cleanup Job (Safety net, every 30 min)

// Runs every 30 minutes
// Finds PENDING records > 1 hour old
// Checks if file exists in MinIO

File exists → RECOVER (upload done, confirm missed)
  → update status UPLOADED
  → trigger processing
  → Tanzania network drop scenario handled ✅

File not exists → ABANDONED (user closed app)
  → update status ABANDONED
  → release quota reservation

Layer 3 — Raw Bucket Lifecycle (Final safety)

nexgate-raw auto-delete: 24 hours
Incomplete multiparts aborted: 24 hours
= catches anything missed by layers 1 + 2

Cleanup Job Scaling

Add DB index:
  CREATE INDEX idx_media_cleanup
  ON media_files (created_at)
  WHERE status = 'PENDING'

Process in batches of 100
Parallel MinIO checks (parallelStream)
Redis distributed lock (prevent overlap):
  SET lock:cleanup_job "running" NX EX 2100

fileId in Object Key (Enables Recovery)

objectKey = uploads/{userId}/{fileId}/original.mp4
                               ↑
                         fileId encoded in path
→ cleanup job extracts fileId from objectKey
→ can recover without client confirm

17. Progress Tracking (SSE)

Why SSE (not polling, not WebSocket)

Polling SSE WebSocket
Direction Both Server→Client only Both
Connection New each time Persistent Persistent
Auto-reconnect Manual Built-in ✅ Manual
Complexity Medium Simple Complex
Tanzania networks Wasteful Resilient ✅ Complex

Upload progress = one direction only → SSE is perfect fit.

Status Flow

Redis key: upload_status:{fileId}

PENDING      → "Upload requested"
UPLOADING    → "Uploading..."
UPLOADED     → "File received"
SCANNING     → "Checking file..."
PROCESSING   → "Processing video..."
LIVE_PARTIAL → "Almost ready!" + { available: ["360p"] }
READY        → "Your post is live!" + { liveUrl: "..." }
FAILED       → "Something went wrong"
QUARANTINED  → "File failed security check"
ABANDONED    → "Upload timed out"

Spring Boot SSE

@GetMapping(
  value = "/media/{fileId}/progress",
  produces = MediaType.TEXT_EVENT_STREAM_VALUE
)
SseEmitter trackProgress(@PathVariable String fileId) {
  SseEmitter emitter = new SseEmitter(7_200_000L); // 2hr
  emitterRegistry.register(fileId, emitter);
  // Send current status immediately
  emitter.send(redis.get("upload_status:" + fileId));
  return emitter;
}

Multi-Instance Scaling

File Thunder (Server A) updates Redis
File Thunder (Server B) has SSE connection
→ Redis Pub/Sub bridges them:
  PUBLISH media_status:{fileId} { status: "READY" }
  Server B receives → finds local emitter → pushes to client

18. Communication Architecture

Rule: No Direct HTTP Between Services

❌ No REST API calls between File Thunder and Main Backend
❌ No webhooks
✅ RabbitMQ for internal operations
✅ Kafka for event streaming to external services

RabbitMQ (File Thunder ↔ Main Backend)

Exchange: nexgate.media (topic exchange)

Routing Key Direction Consumer
media.upload.request MB → FT File Thunder
media.upload.url.ready FT → MB Main Backend
media.ready FT → MB Main Backend
media.live.partial FT → MB Main Backend
media.failed FT → MB Main Backend
media.quarantined FT → MB Main Backend
digital.product.ready FT → MB Main Backend

Example MEDIA_READY event:

{
  "event": "MEDIA_READY",
  "fileId": "vid_789",
  "ownerId": "usr_123",
  "type": "SHORT_VIDEO",
  "status": "READY",
  "variants": {
    "360p_clean": "posts/usr_123/vid_789/360p_clean.mp4",
    "720p_clean": "posts/usr_123/vid_789/720p_clean.mp4",
    "thumbnail": "posts/usr_123/vid_789/thumb.webp",
    "blurhash": "LGF5]+Yk^6#M@-5c,1J5@[or[Q6.",
    "lqip": "data:image/webp;base64,...",
    "dominantColor": "#1a1a2e",
    "preview_3s": "posts/usr_123/vid_789/preview_3s.mp4",
    "og_clean": "posts/usr_123/vid_789/og_clean.webp",
    "og_preview_video": "og/vid_789/og_preview.mp4"
  },
  "isReelEligible": true,
  "streamingFormat": "MP4",
  "duration": 28,
  "aspectRatio": "9:16"
}

Kafka (File Thunder → Rec Engine + Analytics)

Topic: content.new

{
  "event": "FILE_READY",
  "fileId": "vid_789",
  "type": "SHORT_VIDEO",
  "ownerId": "usr_123",
  "media": {
    "duration": 28,
    "aspectRatio": "9:16",
    "qualityScore": 75,
    "isReelEligible": true,
    "hasAudio": true,
    "streamingFormat": "MP4"
  },
  "userProvided": {
    "caption": "Check this Spring Boot setup",
    "hashtags": ["#tech", "#java", "#springboot"],
    "location": null
  },
  "audioRef": {
    "bucket": "nexgate-private",
    "objectKey": "audio/vid_789.wav",
    "expiresAt": "2026-05-23T10:00:00Z"
  },
  "thumbnailUrl": "https://media.nexgate.com/...",
  "processedAt": "2026-05-22T10:00:00Z"
}

Rec Engine consumes this, fetches audio.wav, runs Whisper transcription, classifies content, deletes audio.wav.

19. CDN Strategy

How It Works

First request (cache miss):
  Client → Cloudflare edge → MinIO → Cloudflare caches → serves

Every subsequent request (cache hit):
  Client → Cloudflare edge → serves from cache
  MinIO never touched

Cache-Control Headers

Content Cache-Control TTL
Post thumbnails public, max-age=31536000 1 year
Video MP4 variants public, max-age=31536000 1 year
HLS .ts chunks public, max-age=31536000 1 year
HLS .m3u8 manifests public, max-age=31536000 1 year
OG images public, max-age=31536000 1 year
OG preview video public, max-age=31536000 1 year
Profile pictures public, max-age=86400 1 day
API responses no-store Never cached
Private content private, no-store Never cached

Cloudflare Phases

Phase Setup Cost
Now (launch) Cloudflare Free $0
Growth Cloudflare Pro $20/month
Scale Migrate to Cloudflare R2 (zero egress) Pay storage only

MinIO — Never Publicly Exposed

Public access: BLOCKED
Only Cloudflare IPs can reach MinIO
Client → media.nexgate.com (Cloudflare) → MinIO (internal)
MinIO URL never seen by clients

Share URL Format

Generated client-side (no server call):
  nexgate.com/reels/reel_abc123?ref=whatsapp

ref values:
  whatsapp, telegram, twitter, sms, copy, email

Follow Prompt (On Link Click)

Sarah taps share link
→ NexGate loads post
→ Server looks up post owner from DB (postId → authorId)
→ Shows follow prompt for correct creator
→ No uid in URL (no manipulation possible)
→ No token needed (public content)

Analytics from ref Parameter

Track per share:
  Which platform shared from
  Click-through rate per platform
  Follow conversion rate per platform
  New signups from shares
  Watch completion rate from shares

21. Technology Stack

Component Technology
Language Java 21 (Spring Boot 3.x)
Video processing FFmpeg (global install) via Jaffree
Image processing ImageMagick (global install) via IM4Java
BlurHash blurhash-java library
Virus scanning ClamAV (Docker container, TCP :3310)
Object storage MinIO (S3 compatible)
CDN Cloudflare
Message queue (ops) RabbitMQ
Event streaming Kafka
Cache / progress Redis
Database PostgreSQL
Resumable uploads TUS protocol
Secrets HashiCorp Vault (vault.qbitspark.com)
Container Docker + Docker Compose
Progress delivery SSE (Server-Sent Events)

Why FFmpeg + ImageMagick Global Install

Both are CLI tools (not daemons)
Called on demand via ProcessBuilder
Jaffree/IM4Java call /usr/bin/ffmpeg and /usr/bin/convert
Same filesystem = works perfectly
No network overhead
Simpler than separate containers

ClamAV = separate Docker container because:
  Runs as daemon (long-running process)
  Official Docker image exists
  Connects via TCP = natural for Docker
  Auto-updates virus definitions

22. Database Schema

-- Core media file record
media_files
  file_id           UUID PK
  owner_id          UUID          -- accountId
  directory         ENUM          -- PROFILE, POSTS, STORIES, EVENTS, SHOPS, MESSAGES, PRODUCTS
  original_name     TEXT
  object_key        TEXT          -- raw upload path in nexgate-raw
  mime_type         TEXT
  file_size         BIGINT
  status            ENUM          -- PENDING, UPLOADING, UPLOADED, SCANNING, PROCESSING,
                                  -- LIVE_PARTIAL, READY, FAILED, QUARANTINED, ABANDONED, EXPIRED
  variants          JSONB         -- all processed variant paths
  metadata          JSONB         -- dimensions, duration, fps, codec
  scan_result       TEXT          -- "clean" or virus name
  hash              TEXT          -- SHA-256 for deduplication
  is_reel_eligible  BOOLEAN
  streaming_format  ENUM          -- MP4, HLS
  created_at        TIMESTAMPTZ
  ready_at          TIMESTAMPTZ

-- Content signals for Rec Engine
media_content_signals
  file_id           UUID FK
  has_audio         BOOLEAN
  audio_ref         TEXT          -- nexgate-private/audio/{fileId}.wav
  dominant_color    TEXT          -- hex color
  blurhash          TEXT
  lqip              TEXT          -- base64
  aspect_ratio      TEXT          -- "9:16", "16:9", "1:1", "4:5"
  quality_score     INT           -- 0-100
  width             INT
  height            INT
  duration_seconds  DECIMAL

-- User storage quota
user_storage_quota
  user_id           UUID PK
  plan              ENUM          -- FREE, PRO, BUSINESS
  quota_bytes       BIGINT
  used_bytes        BIGINT
  file_count        INT
  updated_at        TIMESTAMPTZ

-- Per bucket breakdown
user_storage_breakdown
  user_id           UUID
  bucket            TEXT
  used_bytes        BIGINT
  file_count        INT
  updated_at        TIMESTAMPTZ

-- Deduplication hash index
file_hashes
  hash              TEXT PK       -- SHA-256
  object_key        TEXT          -- canonical storage path
  file_size         BIGINT
  mime_type         TEXT
  reference_count   INT
  created_at        TIMESTAMPTZ

-- Variant storage class tracking
media_variants
  file_id           UUID FK
  quality           TEXT          -- "360p", "720p", "1080p", "thumb", etc
  status            ENUM          -- HOT, WARM, COLD, FROZEN
  storage_class     TEXT
  object_key        TEXT
  file_size         BIGINT
  last_accessed     TIMESTAMPTZ
  access_count      INT

-- Digital products
digital_product_files
  file_id           UUID PK
  product_id        UUID FK
  file_type         ENUM          -- MAIN, PREVIEW, COVER
  original_name     TEXT
  mime_type         TEXT
  file_size         BIGINT
  checksum          TEXT          -- SHA-256
  object_key        TEXT
  status            ENUM          -- PROCESSING, READY, FAILED
  created_at        TIMESTAMPTZ

-- Digital orders
digital_orders
  order_id          UUID PK
  product_id        UUID FK
  buyer_id          UUID FK
  seller_id         UUID FK
  amount_paid       DECIMAL
  currency          TEXT
  status            ENUM          -- PAID, REFUNDED, DISPUTED
  download_count    INT DEFAULT 0
  download_limit    INT
  expires_at        TIMESTAMPTZ
  purchased_at      TIMESTAMPTZ

-- Download audit log
digital_download_logs
  log_id            UUID PK
  order_id          UUID FK
  buyer_id          UUID FK
  file_id           UUID FK
  downloaded_at     TIMESTAMPTZ
  ip_address        TEXT
  device_id         TEXT
  user_agent        TEXT
  country           TEXT
  download_number   INT           -- which download (1st, 2nd, etc)

Critical indexes:

-- Cleanup job performance
CREATE INDEX idx_media_cleanup
ON media_files (created_at)
WHERE status = 'PENDING';

-- Hash lookup for deduplication
CREATE UNIQUE INDEX idx_file_hashes_hash
ON file_hashes (hash);

-- Owner lookup
CREATE INDEX idx_media_files_owner
ON media_files (owner_id, status, created_at DESC);

23. Docker & Infrastructure

File Thunder Dockerfile

FROM eclipse-temurin:21-jdk-alpine

# Install FFmpeg (global, called by Jaffree)
RUN apk add --no-cache ffmpeg

# Install ImageMagick with WebP support (called by IM4Java)
RUN apk add --no-cache \
    imagemagick \
    imagemagick-webp \
    imagemagick-heic

# Copy Spring Boot jar
COPY target/file-thunder.jar app.jar

ENTRYPOINT ["java", "-jar", "/app.jar"]

Docker Compose (Relevant Services)

file-thunder:
  build: ./file-thunder
  ports: ["8081:8081"]
  environment:
    SPRING_DATASOURCE_URL: jdbc:postgresql://postgres:5432/nexgate
    SPRING_REDIS_HOST: redis
    RABBITMQ_HOST: rabbitmq
    KAFKA_BOOTSTRAP_SERVERS: kafka:9092
    MINIO_ENDPOINT: http://minio:9000
    CLAMAV_HOST: clamav
    CLAMAV_PORT: 3310
    VAULT_ADDR: https://vault.qbitspark.com
  depends_on: [postgres, redis, rabbitmq, kafka, minio, clamav]

clamav:
  image: clamav/clamav:stable
  ports: ["3310:3310"]
  volumes:
    - clamav_data:/var/lib/clamav
  # Auto-updates virus definitions via freshclam

VPS Resource Allocation

File Thunder: 4 cores, 16GB RAM (FFmpeg is CPU intensive)
ClamAV:       1 core,  2GB RAM

24. What File Thunder Does NOT Do

❌ ML / AI content classification
❌ Speech-to-text (Whisper) — that's Rec Engine
❌ Image visual analysis (CLIP) — that's Rec Engine
❌ Feed computation or ranking
❌ Social graph operations (follow/unfollow)
❌ Payment processing
❌ User authentication / authorization
❌ Push notifications
❌ Search indexing
❌ Business logic (post creation, comments, likes)
❌ Fan-out to followers
❌ Recommendation logic

File Thunder extracts audio.wav and stores temporarily. The Rec Engine fetches it, runs Whisper, classifies content, and deletes the audio file. File Thunder never knows what's in the audio.

Summary — File Thunder in One Sentence

File Thunder receives raw files, validates and secures them via ClamAV, processes them into optimized delivery variants using FFmpeg and ImageMagick, stores everything in MinIO across four isolated buckets, serves public content efficiently via Cloudflare CDN, tracks progress via SSE and Redis, communicates with the Main Backend via RabbitMQ, and publishes content signals to Kafka for downstream services — without ever performing any business logic, ML, or social operations.

File Thunder Architecture Guide v1.0 — NexGate / QBIT SPARK
Document compiled: May 2026

NextGate Media Delivery — Redesign

Target: a safe, scalable media layer for the feed, modelled on patterns observed in TikTok's delivery (signed expiring URLs, CDN edge, variant matrix, batch minting) and mapped onto NextGate's existing media engine (MinIO + RabbitMQ + workers + Redis).

1. What's wrong today

Observed in the current GET /posts (feed) response.

# Problem Why it matters
1 originalUrl is a raw, permanent, unsigned link to s3.nexgate.co Post visibility is enforced at the API only. A PRIVATE post's bytes stay reachable at a permanent public URL → media bypasses access control entirely.
2 Storage origin exposed, no CDN Every view hits MinIO directly. High latency from East Africa, full egress cost, zero edge cache.
3 thumbnailUrl: null, placeholderBase64: null Full-res images (e.g. 1536×2048) served into feed thumbnail slots. Heavy on expensive mobile data. Blurhash field exists but unused.
4 Video = raw .mp4, width/height/duration = null No transcode, no poster frame, no ladder, no HLS. No adaptive playback.
5 Per-user path prefix doesn't match owner e.g. joshdoe's avatar stored under eddiesmith19's stg-acc-{uuid} prefix. Leaks UUIDs and misattributes ownership.
6 dev.s3.nexgate.co leaking into staging data Environment bleed in a live feed response.

What to KEEP (already good): batch-hydrated feed (one call, all posts + nested quotes + engagement), permanent shareCode short IDs, graceful deleted-post handling (unavailable: true), the rich post data model.

The fix is scoped to the media delivery layer, not the data model.

2. Core principle

Two URLs, two lifespans (same split TikTok uses):

Rule: store the objectKey, never store the signed URL.

3. Three delivery tiers

Tier Content Auth gate? URL signing Expiry CDN cache
1 — public asset avatars, thumbnails no none (or very long) n/a / long aggressive, long TTL
2 — public content, protected delivery public post images/video no yes (short-ish) hours careful (see §6)
3 — private content private/followers posts, paid digital yes (ownership/visibility check) yes minutes none / private

The only code difference between tier 2 and tier 3 is whether the permission check runs before minting. Same minting call underneath.

4. Storage layer changes

4.1 Buckets

Shared buckets, owner-prefixed object keys, prefix must match the real owner. Opaque object keys — no user UUID needed in the public URL.

private/{ownerId}/{mediaId}/original.jpg
private/{ownerId}/{mediaId}/thumb_320.webp
private/{ownerId}/{mediaId}/thumb_720.webp

4.2 DB: store keys, not URLs

Persist the storage coordinates and processing state, not a full URL.

// ── MediaEntity (delivery-relevant fields) ──
private String bucket;          // "private"
private String objectKey;       // "ownerId/mediaId/original.jpg"  (opaque, owner-correct)
private MediaType mediaType;    // IMAGE | VIDEO
private Integer width;
private Integer height;
private Double  duration;       // video only
private String  placeholder;    // blurhash / LQIP — fills the empty placeholderBase64
private MediaStatus status;      // PROCESSING | READY | FAILED
// variants: thumb sizes, video rungs, formats — JSONB
private String variantsJson;     // {"thumb":["320","720"],"formats":["webp"],"rungs":[...]}

5. Delivery layer changes

5.1 CDN in front of MinIO

Serve everything through media.nexgate.co (Cloudflare) → MinIO origin. Never return s3.nexgate.co (or dev.s3…) in an API response again.

5.2 Minting helper (SDK does the crypto)

// ── Presigned URL minting (MinIO SigV4) ──
public String mintUrl(String bucket, String objectKey, int seconds) {
    return minioClient.getPresignedObjectUrl(
        GetPresignedObjectUrlArgs.builder()
            .method(Method.GET)
            .bucket(bucket)
            .object(objectKey)
            .expiry(seconds, TimeUnit.SECONDS)   // → X-Amz-Expires + X-Amz-Signature
            .build());
    // returned host is rewritten to media.nexgate.co at the edge / via MinIO public endpoint
}

5.3 Feed response shape (mint at build time, batch)

Mirror TikTok's batch mint: build the page, mint every media URL inline, ship once. No per-item round trip from the client.

"media": [{
  "id": "014ab4eb-...",
  "mediaType": "IMAGE",
  "url": "https://media.nexgate.co/.../original.jpg?X-Amz-Expires=3600&X-Amz-Signature=...",
  "thumbnailUrl": "https://media.nexgate.co/.../thumb_720.webp?...sig...",
  "placeholderBase64": "LEHV6nWB2yk8...",   // blurhash, no longer null
  "width": 945, "height": 2048,
  "expiresIn": 3600
}]

// ── In the feed mapper ──
String url   = mintUrl(m.getBucket(), m.getObjectKey(), tier2Seconds);          // hours
String thumb = mintUrl(m.getBucket(), thumbKey(m, 720),  tier2Seconds);
// tier 3 (private/paid): run accessService.canAccess(user, m) first, use short expiry

6. CDN + signed-URL gotcha

Do not let the CDN cache a per-user signed URL under a key that includes the signature, or one user's link can be served to another. Options:

Tier 1 assets are the ones you cache aggressively. Tier 3 never shares cache.

7. Variant + transcode pipeline (reuse existing media engine)

On upload (presigned PUT direct to MinIO → enqueue job → workers → webhook back):

Until a media row is READY, the feed returns the blurhash placeholder + a processing flag instead of a broken/raw link.

8. Migration sequence (non-breaking)

  1. CDN — stand up media.nexgate.co → MinIO, dual-serve. Stop emitting s3.nexgate.co.
  2. Schema — add bucket/objectKey/status/placeholder/variantsJson. Backfill objectKey by parsing existing originalUrl; fix owner prefix + drop dev. rows here.
  3. Mint — change feed to mint from objectKey instead of returning raw originalUrl. Roll out tier 1 + tier 2 first (public) so nothing visibly breaks.
  4. Backfill variants — run image/video workers over existing media; populate thumbs + blurhash.
  5. Lock the bucket — remove public-read from MinIO; force all access through signed CDN URLs. At this point the visibility-bypass hole (problem #1) is closed.
  6. Tier 3 — gate private/followers/paid media behind canAccess + short expiry.

Closing problem #1 happens at step 5; everything before it is safe groundwork.

9. Security checklist ("safe" part)

File Thunder — Architecture & Design Guide V2

NexGate Media Engine | Version 2.0

v2 integrates the media-security refinements worked out in design review. Every change from v1 is tagged inline as [v2 FIX] so it can be reviewed individually. Section 0 lists all of them in one place — read that first.

0. What changed in v2 (read this first)

These are the careful corrections. Each is explained in full in its section.

  1. Signing is three tiers, not two. "Public = unsigned, private = signed" was wrong. Correct model: trivial public assets unsigned; public content (full images/videos) signed even though public; private/paid signed + auth. → §8
  2. Public content gets signed too. A signed URL is anti-scrape / anti-hotlink, not only access control. TikTok signs even public videos. → §8, §14
  3. The visibility-bypass hole must be closed. In v1, media URLs were permanent and unsigned, so a PRIVATE post's bytes were reachable by anyone with the link — the post was hidden by the API but the file was not. Fixed by locking the bucket (no public-read) and routing everything through signed CDN URLs. → §14
  4. Backend signs, CDN validates, they never talk at sign time. Signing is pure math on (path + expiry + secret). No file, no CDN contact. CDN fetches from MinIO lazily on first view. → §9
  5. Domain is media.nexgate.co, not .com. v1 mixed both. One domain everywhere. → §10
  6. Object keys must be owner-correct. v1 had one user's avatar stored under another user's prefix. The owner segment in the key must match the real owner. → §3
  7. Store the objectKey, never the signed URL. Signed URLs are minted per request and thrown away. Never persisted in the DB or feed cache. → §13, §22
  8. MP4 and HLS use different token strategies. Short MP4 = one signed URL. Long HLS = dual-token (short manifest + long segments) or prefix-signing, so playback never dies mid-video. → §11
  9. Single-use is for downloads only, never streams. A stream is many requests; single-use would break playback. Streams use short expiry + user-binding instead. → §11, §12
  10. Watermarked file is NEVER in the feed response. Feed = clean playback URLs only. Watermarked download comes from a separate endpoint, minted on tap. → §12, §13
  11. Cache gotcha: never cache a signed object keyed by its signature. A cached object can outlive its stamp; private/paid content must bypass shared cache. → §10, §11
  12. Bot gate is the missing half of anti-scraping. Signed URLs stop permanent theft; the bot gate stops the act of mass-pulling. v1 had no bot gate section. → §14
  13. Open decision parked: NextGate's moat (content vs commerce) drives how hard to stamp public media and how heavy the bot gate needs to be. → §30

1. What is File Thunder?

File Thunder is NexGate's dedicated media processing engine — a standalone Spring Boot microservice responsible for all file and media operations across the platform.

Core principle: The Main Backend never touches raw files. It delegates all media operations to File Thunder and acts as a thin client.

Responsibilities: receive uploads, validate (type/size/quota), virus scan, transcode, generate variants (thumbnails, WebP, HLS, MP4), watermark, store in MinIO, serve via CDN, mint signed delivery URLs, publish media-ready events.

Not: AI/ML, recommendation, social graph, payments, auth, business logic.

2. The Four Wheels

                        FILE THUNDER
        ┌───────────┬───────────┬───────────┬───────────┐
        │  FFmpeg   │ ImageMagic│  ClamAV   │   MinIO   │
        │  (video)  │ (images)  │ (security)│ (storage) │
        └───────────┴───────────┴───────────┴───────────┘
         transcode    resize +    virus       object
         HLS, w/mark  WebP, blur  scan        store + CDN

3. Storage Architecture (MinIO Buckets)

Rule: 4 buckets total. Never one bucket per user.

nexgate-raw/       ← temporary upload landing (auto-delete 24h)
nexgate-public/    ← social content (avatars, posts, stories, events, shops)
nexgate-private/   ← DMs, documents, KYC, temp audio
nexgate-digital/   ← purchase-gated products

Object Key Pattern

{bucket}/{domain}/{ownerId}/{entityId}/{fileId}/{variant}

nexgate-public/posts/usr_123/post_456/file_789/720p_clean.mp4
nexgate-private/messages/conv_abc/file_789/original.jpg
nexgate-digital/products/shop_xyz/prod_123/file_789/original/file.pdf

[v2 FIX] Owner-correct keys. The {ownerId} segment MUST be the real owner of the file. v1 had cases where one user's avatar lived under a different user's prefix — that leaks identity and misattributes ownership. The owner in the key = the owner in the DB. Keys are otherwise opaque (no usernames, no PII).

nexgate-public layout (unchanged from v1)

profiles/{userId}/{fileId}/  avatar_400.webp, avatar_150.webp, avatar_50.webp, cover.webp
posts/{userId}/{fileId}/     {360,720,1080}p_clean.mp4, {360,720,1080}p_watermarked.mp4,
                             preview_3s.mp4, hls/master.m3u8, hls/{360,720,1080}p/seg_*.ts,
                             thumbnail.webp, og_clean.webp, og_play.webp, og_preview.mp4
stories/{userId}/{fileId}/   720p_clean.mp4, thumbnail.webp
events/{accountId}/{eventId}/{fileId}/  banner.webp, banner_mobile.webp, banner_thumb.webp
shops/{shopId}/{productId}/{fileId}/    large.webp, medium.webp, thumb.webp

(See §12 for the watermarked-variant storage decision — store one rung, not all three.)

nexgate-private / nexgate-digital

As v1: messages, documents, kyc, temp audio (private); products with original/ (never exposed) + preview/ + cover/ (digital).

4. Accepted File Formats

5. Upload Flow

[1] Client-side intelligent compression (max 1080p, CRF 18 light, HEIC→JPEG)
[2] POST /media/upload-request { fileName, fileSize, mimeType, directory, clientMeta }
[3] File Thunder: validate MIME + size + quota (atomic SQL) → DB record PENDING
    → presigned MinIO URL (nexgate-raw) → { fileId, uploadUrl, expiresIn: 1800 }
[4] Client uploads directly to MinIO (TUS resumable / multipart >5MB)
[5] Client confirms POST /media/confirm { fileId }   (cleanup job recovers if missed)
[6] Processing pipeline starts

  client compress
        │
        ▼
  POST upload-request ──▶ validate + quota ──▶ presigned URL
        │
        ▼
  upload direct to MinIO (raw)
        │
        ▼
  confirm ──▶ ClamAV ──▶ dedup ──▶ process ──▶ READY
                                      │
                                      ▼
                            RabbitMQ media.ready ──▶ Main Backend

Quota checked at presigned-URL time (atomic UPDATE ... WHERE used+size <= quota). Duration checked AFTER upload via FFprobe (client value is a hint, not trusted) — over limit → delete from raw, release quota, 403 DURATION_EXCEEDED.

Per-Upload Limits

Plan Image Short Video Long Video Digital Video Duration
FREE 20MB 200MB ❌ ❌ 5 min
PRO 20MB 500MB 2GB 5GB 60 min
BUSINESS 20MB 2GB 5GB 20GB Unlimited

6. Processing Pipelines (summary)

All pipelines: ClamAV scan → SHA-256 dedup check → process → store → delete raw → DB READY → publish events. Watermarking and all placeholders are generated here, at processing time, never at serve time.

6.1 Image

Auto-orient → strip EXIF (privacy) → NSFW check → dominant color + LQIP + BlurHash → size variants per content type (Post: 1600/800/300; Profile: 400/150/50; Product: 1000/500/200 square; Event: 1200×630/800×420) → WebP → OG image → store public → READY.

6.2 Short Video (MP4, duration < 3 min)

FFprobe → adaptive transcode decision (never upscale, never inflate) → fast lane (quick 360p → LIVE_PARTIAL) → full processing:

6.3 Long Video (HLS, duration ≥ 3 min)

Same as short EXCEPT: HLS adaptive (no fast lane — stays PROCESSING until done). hls/{360,720,1080}p/ segments + master.m3u8. Segment = 2s, H.264 + AAC, MPEG-TS. Still makes preview_3s, thumbnail, placeholders, OG. isReelEligible: false, streamingFormat: HLS.

6.4 Digital Products

Double ClamAV scan → SHA-256 checksum → light preview by type (PDF p1 watermarked, video first 2min 480p watermarked, audio 30s 96kbps, 3D multi-angle thumbs, image 600px watermarked) → store original/ (never exposed) + preview/ + cover/ → READY.

6.5 DM Attachments

nexgate-private, no CDN, conversation-membership check, thumb+original only, no watermark, no reel pool, signed 5-min URLs. Virus scanned like everything.

7. Watermarking Strategy

[v2 FIX] Honest scope. A watermark does NOT prevent download — it survives download. Its job is attribution + traceability, not prevention. The clean file is reachable by a determined ripper via the playback URL; that's accepted. Goal = "not worth the effort for 99% + traceable if they do."

8. The Three Delivery Tiers [v2 FIX — core correction]

v1 assumed two levels (public unsigned / private signed). Correct model is three:

Tier Content Login to view? URL signed? Expiry CDN cache
1 — trivial public avatars, thumbnails, posters, blur previews no no n/a aggressive, 1y
2 — public content full post images, video rungs no YES hours careful (§10)
3 — private / paid DM media, private posts, digital products, KYC yes YES minutes none / private 
  ┌──────────────────────────────────────────────┐
  │  TIER 1  trivial public                       │
  │  avatars, thumbs    →  unsigned, cache 1y     │
  ├──────────────────────────────────────────────┤
  │  TIER 2  public content                       │
  │  full images/video  →  SIGNED, hrs TTL        │
  ├──────────────────────────────────────────────┤
  │  TIER 3  private / paid                       │
  │  DM, private, digital → SIGNED + auth + x-uid │
  └──────────────────────────────────────────────┘
   only diff T2 vs T3 = auth check before minting

The key insight: "public to view" and "signed URL" are independent. Tier 2 content is open to watch by anyone (no login), but the file is still signed — because signing is anti-scrape / anti-hotlink, not access control. This is exactly TikTok's model (public video, yet the raw file link expires and 403s).

The only difference between tier 2 and tier 3 in code is whether an auth/visibility check runs before minting — the signing itself is identical.

Tier 1 is the only unsigned tier. Anything a scraper would actually want (full media) is tier 2+, i.e. signed.

9. Signed URLs — how they actually work [v2 — new, the mechanism]

A signed URL = a normal link with a stamp made from three things:

stamp (x-sig) = HMAC(secret, path + expiry)

Who does what, and when — three separate moments:

  1. Upload time: File Thunder makes the variants, stores them in MinIO. CDN not involved.
  2. Feed-build time (signing): backend computes x-sig from (path + expiry + secret). Pure string math — no file opened, no CDN contacted, no storage touched. It's just writing a stamped link. (You can sign a path whose bytes don't even exist yet — the math only sees the string.)
  3. Playback time (serving): the phone requests the stamped URL → CDN re-computes the stamp with its copy of the secret. Match + not expired → serve. First viewer: CDN lazily fetches the file from MinIO and caches it. Later viewers: served from cache.
   upload                feed build               playback
  ┌────────┐  store    ┌──────────┐  stamped   ┌──────────┐
  │  File  │ ───────▶  │ Backend  │ ─ link ──▶ │   CDN    │
  │ Thunder│  to MinIO │ signs    │            │ validates│
  └────────┘           └──────────┘            └────┬─────┘
                       secret ▲                      │ first view
                       Vault  └──────── same ────────┘ fetch+cache
                                       secret           from MinIO

Tamper resistance (why a stripped/edited link fails):

Forging anything requires the secret, which never leaves backend + CDN. Protect the secret (Vault) and the whole scheme holds.

You don't write the HMAC. The MinIO SDK (or CDN signer) does it in one call:

// ── Mint a signed delivery URL ──
String url = minioClient.getPresignedObjectUrl(
    GetPresignedObjectUrlArgs.builder()
        .method(Method.GET)
        .bucket(bucket)
        .object(objectKey)
        .expiry(seconds, TimeUnit.SECONDS)   // → x-expires + x-sig
        .build());

10. URL Strategy

Tier 1 — trivial public → permanent, unsigned, cache hard

https://media.nexgate.co/profiles/usr_123/avatar_400.webp
https://media.nexgate.co/posts/usr_123/vid_789/thumbnail.webp

Cache-Control: public, max-age=31536000. Scraping these gains nothing.

Tier 2 — public content → signed, short-ish expiry

https://media.nexgate.co/posts/usr_123/vid_789/720p_clean.mp4?x-expires=1780297200&x-sig=8f3a9c

Tier 3 — private / paid → signed + user-bound + auth check first

https://media.nexgate.co/private/messages/conv_abc/file_789/original.jpg
   ?x-expires=...&x-sig=...&x-uid=usr_xyz

[v2 FIX] Domain is .co. All URLs use media.nexgate.co. v1 mixed .com/.co — that produces broken links. One domain everywhere.

[v2 FIX] Cache-key gotcha. Never let the CDN cache a signed object using a cache key that includes x-sig/x-uid — you'd fragment cache per user, and a cached object can outlive its stamp (origin checks expiry, but a cache hit never reaches origin). Rules: tier 1 cache hard; tier 2 cache by path only (strip query from cache key), short edge TTL; tier 3 never on shared cache.

Signed URL params

Param Purpose
x-expires link dies after TTL
x-sig HMAC tamper protection
x-uid bound to user (tier 3) — shared link won't work for someone else

Who generates / validates

Backend (has secret) generates. Cloudflare edge (same secret) validates. MinIO never seen by clients.

11. Streaming Token Strategy: MP4 vs HLS [v2 — new]

Expiry is checked when each request opens, not continuously. An in-flight transfer completes even if the clock passes mid-download. The two formats differ because of how many requests a single playback makes.

  SHORT MP4                        LONG HLS
  one request                      hundreds of requests
  ┌──────────┐                     ┌──────────┐  ┌──┬──┬──┬──┐
  │ 720p.mp4 │  ← 1 signed URL     │master.m3u│─▶│ts│ts│ts│..│
  └──────────┘     few-hr TTL      └──────────┘  └──┴──┴──┴──┘
  opens once,                      short token     long token
  rides to end                     (~1 min)        (> video len)
                                   per-session      one, shared

Short video (MP4) — one signed URL

One file = one request (or a few byte-ranges, all opened up front). A few-hour expiry is plenty; the in-flight request completes, so mid-play expiry basically never happens. → mint one signed URL per rung, few-hour TTL. No dual-token, no single-use.

Long video (HLS) — dual-token (or prefix-signed)

HLS = hundreds of segment requests (one every ~2s), so expiry is re-checked constantly. A single short token would die mid-video. Industry-standard fix (Google Media CDN / CloudFront):

At our stage on Cloudflare Free/Pro, do the simpler version: backend mints a long prefix-signed token for the whole hls/ folder when the post loads. Graduate to true edge dual-token (short→long exchange) if/when we move to a heavier CDN.

Single-use — downloads ONLY, never streams

A stream is many requests; making the token single-use would 403 the viewer one segment in. Streams use short expiry + x-uid binding instead. Single-use (Redis) is correct only for one-file-one-request downloads (§12, digital products).

Edge case (both formats)

User pauses past expiry, then seeks → player fires a fresh request with a dead URL → 403. Client safety net: catch the 403, silently re-fetch a fresh URL from backend, resume.

Short MP4 Long HLS
Requests / play one (few byte-ranges) hundreds
Token single signed URL dual-token / prefix-signed
TTL few hours > watch duration
Single-use no no

12. Watermark & Download Path [v2 FIX]

Decision: Option B — downloads are watermarked. (Full build, not the launch shortcut.)

The feed NEVER contains a watermarked URL. Feed = clean playback URLs only. Watermarked download is a separate endpoint, minted on tap.

User taps Download
  → GET /media/{fileId}/download?quality=720p   (quality optional, default 720p)
  → backend: check canDownload (post setting) + tier (private/paid → auth check)
  → mint signed URL → {quality}_watermarked.mp4
       short TTL (~10 min), x-uid bound, single-use (Redis x-once)
  → log download event (orderId/buyerId/ip/device/country if digital)
  → return { downloadUrl, expiresIn, singleUse: true }
Client downloads. URL marked used in Redis → 403 on reuse.

Default quality, no picker (short video). Serve one default rung (720p) — matches TikTok/IG, sane on TZ data. Endpoint takes optional quality so a picker is an additive change later (long-form only, where the size gap matters).

Storage decision: store one watermarked rung (720p), not all three. If a picker is added later, lazy-generate other rungs on first request and cache — only spend CPU/storage on a quality someone actually downloads.

Timing: watermarked 720p is generated at processing time (pre-ready), so download is instant — no first-user FFmpeg penalty.

// ── Download endpoint (picker-ready, single-use, watermarked) ──
@GetMapping("/media/{fileId}/download")
ResponseEntity<?> download(@PathVariable String fileId,
                           @RequestParam(defaultValue = "720p") String quality,
                           @AuthenticationPrincipal AccountEntity user) {
    MediaEntity m = mediaService.findReady(fileId);

    // ── access gate (tier 2 = open; tier 3 = ownership/visibility) ──
    if (!m.isCanDownload())                 return ResponseEntity.status(403).build();
    if (m.isRestricted() && !accessService.canAccess(user, m))
                                            return ResponseEntity.status(403).build();

    // ── mint watermarked, user-bound, single-use URL ──
    String key = m.watermarkedKey(quality);                 // lazy-generate if absent
    String url = mediaService.mintDownloadUrl(key, user.getId(), Duration.ofMinutes(10));
    downloadLog.record(fileId, user, request);              // audit
    return ResponseEntity.ok(Map.of("downloadUrl", url, "expiresIn", 600, "singleUse", true));
}

13. Feed Response Shape [v2 — new]

Rules baked in:

{
  "data": [{
    "id": "0e67aef4-...",
    "author": {
      "id": "ad03431a-...", "userName": "juliusdev_", "verified": true,
      "profilePictureUrl": "https://media.nexgate.co/profiles/ad03431a-.../avatar_400.webp"
    },
    "content": "Testing video media post 🎬",
    "shareCode": "waBbP82h",
    "media": [{
      "id": "436bb62b-...",
      "mediaType": "VIDEO",
      "status": "READY",
      "width": 1080, "height": 1920, "aspectRatio": "9:16", "duration": 28,
      "isReelEligible": true,
      "streamingFormat": "MP4",
      "canDownload": true,
      "dominantColor": "#1a1a2e",
      "blurhash": "L6Pj0^i_.AyE_3t7t7R**0o#DgR4",
      "lqip": "data:image/webp;base64,UklGRjoAAAB...",
      "poster":    "https://media.nexgate.co/posts/ad03431a-.../436bb62b-.../thumbnail.webp",
      "preview3s": "https://media.nexgate.co/posts/ad03431a-.../436bb62b-.../preview_3s.mp4",
      "variants": {
        "360p":  "https://media.nexgate.co/posts/ad03431a-.../436bb62b-.../360p_clean.mp4?x-expires=1780297200&x-sig=a1f2b3",
        "720p":  "https://media.nexgate.co/posts/ad03431a-.../436bb62b-.../720p_clean.mp4?x-expires=1780297200&x-sig=b2e3c4",
        "1080p": "https://media.nexgate.co/posts/ad03431a-.../436bb62b-.../1080p_clean.mp4?x-expires=1780297200&x-sig=c3f4d5"
      },
      "order": 1
    }],
    "privacySettings": { "visibility": "PUBLIC" }
  }]
}

(HLS video: streamingFormat: "HLS", replace variants with a single signed/prefix-signed master.m3u8.)

14. Security & Anti-Scraping [v2 — expanded]

14.1 Close the visibility-bypass hole

v1's permanent unsigned URLs meant a PRIVATE post's bytes were reachable by anyone with the link — the API hid the post, the file did not. Fix:

  1. Remove public-read from MinIO buckets (already a stated rule — enforce it).
  2. Route all access through signed CDN URLs.
  3. Private/followers/DM/paid → tier 3 (auth check before minting + x-uid). After this, a hidden post's media returns 403 to anyone but the authorized viewer.

14.2 Two layers, both required

14.3 Bot gate (the missing half) — sized to moat (§30)

Build depth depends on the moat decision (§30). Commerce-moat → lighter bot gate is fine for launch. Content-moat → invest earlier.

14.4 Protection layers (reference)

Content-Disposition: inline · dynamic URL via JS · signed expiring URLs · session/device binding · disable right-click (frontend) · watermark on download · HLS chunking.

15. OG (Open Graph) Strategy

OG images + og_preview.mp4 are permanent, unsigned, tier 1 — because crawlers (WhatsApp/Telegram) fetch on share and the user may open hours later; a signed URL would expire → "Error loading." Access control for private posts is enforced server-side (the post page returns 403), not via the OG asset. Serve og_clean.webp to known platforms, og_play.webp (burned play button) to unknown crawlers (User-Agent detection).

16. Compression & Transcoding (reference)

Client: light pre-compress (max 1080p, CRF 18, never upscale). Server: FFprobe → adaptive ladder (never upscale, never inflate → -c:v copy if output > input). CRF 21/23/25/28 for 1080/720/480/360, 30 for OG preview. 1080p max (all platforms serve ≤1080p anyway). -movflags +faststart always; frag_keyframe+empty_moov+faststart for fMP4. Now: H.264 + AAC. Future: AV1 + Opus + CMAF.

17. BlurHash, LQIP & Dominant Color

Generated for every image + video thumbnail, at processing time. Progressive load: dominantColor (0ms) → BlurHash (0ms) → LQIP (0ms) → thumb.webp (CDN) → full on tap. All three stored in media_content_signals and shipped inline in the feed JSON.

18. Deduplication

SHA-256 on raw file → file_hashes. Exists+clean → skip processing, reference existing variants, reference_count++. Delete → decrement; 0 → remove from MinIO. Near-dup (pHash) = future (copyright).

19. Quota Management

Enforced at presigned-URL generation (atomic SQL). Social = original size charged; digital = all stored bytes. Plans: FREE 1GB / PRO 20GB / BUSINESS 100GB. Warn 80%/95%/100%. Release on abandoned (immediate) and hard-delete (30d after soft). Redis cache, sync to PG every 5 min.

20. Storage Lifecycle

raw: auto-delete 24h. public: keep forever, access-based tiering (hot NVMe → warm HDD → cold; viral old content auto-promotes). private: DM 1y, audio 24h, KYC per law. digital: forever. Soft delete → 30d grace → hard delete + Cloudflare purge + quota free.

21. Abandoned Upload Handling

Layer 1: client confirm (fast path). Layer 2: cleanup job every 30 min (PENDING >1h → file exists = recover/process; not = abandoned, release quota). Layer 3: raw lifecycle 24h. fileId in object key enables recovery without confirm. Redis distributed lock on the job.

22. Progress Tracking (SSE)

SSE (one-way, auto-reconnect, resilient on TZ networks). Redis key upload_status:{fileId}: PENDING→UPLOADING→UPLOADED→SCANNING→PROCESSING→LIVE_PARTIAL→READY (or FAILED/QUARANTINED/ ABANDONED). Multi-instance via Redis Pub/Sub bridging emitters.

23. Communication Architecture

No direct HTTP between services. RabbitMQ (FT ↔ Main Backend, topic nexgate.media): media.upload.request, media.upload.url.ready, media.ready, media.live.partial, media.failed, media.quarantined, digital.product.ready. Kafka (FT → Rec Engine / Analytics, topic content.new).

[v2 FIX] Events carry objectKeys + variants, not signed URLs. MEDIA_READY ships storage keys (e.g. posts/usr_123/vid_789/720p_clean.mp4) + placeholders. The Main Backend mints signed URLs per feed request from those keys — it never stores a signed URL.

24. CDN Strategy

Cloudflare in front of MinIO. First request → edge → MinIO → cache → serve; thereafter from cache. Cache-Control: tier 1 = 1y; tier 2 = path-keyed short edge TTL; tier 3 / API = private, no-store. MinIO never publicly exposed (only Cloudflare IPs). Phases: Free → Pro ($20) → R2 (zero egress). See §10 cache-key gotcha.

Client-side nexgate.co/reels/{shareCode}?ref=whatsapp. No uid in URL (server resolves owner from shareCode → follow prompt). ref drives share analytics. Public content = no token needed for the page; the media on the page still follows tier rules (§8).

26. Technology Stack

Java 21 / Spring Boot 3.x · FFmpeg (Jaffree) · ImageMagick (IM4Java) · blurhash-java · ClamAV (Docker, TCP 3310) · MinIO · Cloudflare · RabbitMQ · Kafka · Redis · PostgreSQL · TUS · Vault (vault.qbitspark.com) — holds the signing secret · Docker Compose · SSE.

27. Database Schema (key tables + v2 notes)

media_files (
  file_id UUID PK, owner_id UUID, directory ENUM, original_name TEXT,
  object_key TEXT,          -- canonical storage key  [v2: keys, never signed URLs]
  mime_type TEXT, file_size BIGINT,
  status ENUM,              -- PENDING..READY..QUARANTINED..ABANDONED
  variants JSONB,           -- variant object_keys (NOT URLs)
  metadata JSONB, scan_result TEXT, hash TEXT,
  is_reel_eligible BOOLEAN, streaming_format ENUM,
  can_download BOOLEAN DEFAULT true,   -- [v2] drives feed canDownload + download gate
  created_at TIMESTAMPTZ, ready_at TIMESTAMPTZ
);

media_content_signals (
  file_id UUID FK, has_audio BOOLEAN, audio_ref TEXT,
  dominant_color TEXT, blurhash TEXT, lqip TEXT,
  aspect_ratio TEXT, quality_score INT, width INT, height INT, duration_seconds DECIMAL
);

-- user_storage_quota, file_hashes, media_variants (HOT/WARM/COLD),
-- digital_product_files, digital_orders, digital_download_logs  (as v1)

Indexes: idx_media_cleanup (created_at) WHERE status='PENDING'; unique file_hashes(hash); media_files(owner_id, status, created_at DESC).

[v2 FIX] No signed_url column anywhere. Signed URLs are minted per request and discarded. The DB stores only object_key + variants (keys).

28. Docker & Infrastructure (reference)

eclipse-temurin:21 + ffmpeg + imagemagick(+webp/heic). ClamAV separate container (daemon, auto-updates). FT: 4 cores / 16GB (FFmpeg CPU-heavy). ClamAV: 1 core / 2GB. Env: PG, Redis, RabbitMQ, Kafka, MinIO, ClamAV, VAULT_ADDR.

29. What File Thunder Does NOT Do

❌ ML/AI classification · Whisper (Rec Engine) · CLIP · feed ranking · social graph · payments · auth · push · search · business logic · fan-out · recommendations. Extracts audio.wav temporarily; Rec Engine fetches/transcribes/deletes. FT never knows audio content.

30. Open Decisions (parked)

  1. Moat: content vs commerce? This drives §14.3 (bot-gate depth) and §8 (how hard to stamp tier-2 public media). If commerce is the moat (shops/payments/events), public media scraping hurts less → lighter bot gate, tier-2 stamping is softer/optional. If content is the moat → invest in bot gate + stamp tier-2 firmly. Decide before finalizing anti-scraping work.
  2. Bot gate depth for launch — minimum: login + rate limit. Full app-attestation later, sized to (1).
  3. HLS dual-token vs prefix-sign for launch — prefix-sign on Cloudflare now; edge dual-token if/when heavier CDN (§11).
  4. Download quality picker — default 720p now; picker + lazy-gen later (§12).

Summary — File Thunder v2 in one line

Receives raw files → ClamAV → processes into clean + watermarked variants (FFmpeg/IM) with blurhash/lqip/dominant-color → stores object keys across 4 buckets in MinIO (never public-read) → the Main Backend mints signed delivery URLs per request from those keys using a three-tier policy (trivial-public unsigned, public-content signed, private/paid signed + auth) → Cloudflare serves and caches by tier → streams use MP4-single-URL or HLS-dual-token, downloads use single-use watermarked URLs → signed URLs + a bot gate together make scraping not worth the effort — all without business logic, ML, or social ops.

File Thunder Architecture Guide v2.0 — NexGate / QBIT SPARK v2 integrates media-security design review. [v2 FIX] tags mark every change from v1.